# Finding the Image of a point

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• Sep 15th 2012, 01:09 PM
sakonpure6
Finding the Image of a point
Hi i need help with the following question:

The point(1,4) is on the graph of y= f(x). Determine the coordinates of the image of this point on the graph of y=3f[-4(x+1)]-2.

What i tried was plunging in 4 for y and 1 for x and solving for the image but i did not get the correct answer which is (-5,10) from my book.

Edit: what does it mean by "image" ?
• Sep 15th 2012, 02:00 PM
skeeter
Re: Finding the Image of a point
sure it's not $\displaystyle \left(-\frac{5}{4} , 10\right)$ ?
• Sep 15th 2012, 02:05 PM
sakonpure6
Re: Finding the Image of a point
can you tell me what you did and how you did it please! because this is what i got 4=3f(-8)-2 and im kind of stuck there
• Sep 15th 2012, 02:12 PM
HallsofIvy
Re: Finding the Image of a point
"(1, 4) is on the graph of y= f(x)" means that f(1)= 4. In order to use "f(1)= 4", to calculate $\displaystyle 3f(-4(x+1))- 2$, we must have $\displaystyle -4(x+1)= 1$ which is the same as x= -5/4. And then, $\displaystyle 3f(-4(x+1)- 2= 3f(1)- 2= 3(4)- 2= 10$.
• Sep 15th 2012, 02:25 PM
sakonpure6
Re: Finding the Image of a point
Oh okay I understand now, thank you so much because I'm pretty sure this is going to be on my math test!